This invention relates to zone-type range-detecting devices used for automatically adjusting the focus of cameras.
As is well known, there are many kinds of range-detecting devices for detecting a zone in which an object to be photographed is located, such as the extreme value detection type, the coincidence type, or the gravity influenced pendulum type. The respective types of range-detecting device are further divided into two categories, in one of which it is necessary to provide mechanical, optical or electric scanning means and in the other of which it is not necessary to have any scanning means.
Cameras with a range-detecting device without any incorporated scanning means are not only advantageous in design but also easy to operate. Moreover, an increase in the number of range-detecting means is unavoidable as the number of zones in response to which a camera's picture-taking lens is adjusted increases.
Such an increased number of range-detecting means is economically disadvantageous and provides unsatisfactory accuracy. A zone-type range-detecting device which has been proposed to eliminate the above-mentioned disadvantages is described in U.S. Pat. No. 3,945,023. In that patent, a zone-type range-detecting device is provided with a first array of light-sensing elements for receiving light from an object along a first optical light path and a second array of light-sensing elements for receiving light from the object along a second optical light path, and the disagreement between intensity distributions of light on the first and second means is detected so as to find the zone within which the object to be photographed is located. However, in such a range-detecting device, there are the disadvantages that, since an increased number of circuit elements is required in order to detect the degree of disagreement between the intensity distribution of light on the first and second means, the range-detecting devices become complicated in construction, and detection failure can result from patterns of the image of the object on the first and second means.